Conventionally, rotary fluid machines are known. In such a rotary fluid machine, a cylinder with an annular cylinder chamber, and an annular piston arranged in the cylinder chamber eccentrically rotate relative to each other. In the rotary fluid machine, the annular cylinder chamber is divided into inner and outer chambers by the annular piston, and each of such chambers serves as a fluid chamber in which fluid is compressed or expanded. Further, each of the fluid chambers is divided into low-pressure and high-pressure chambers by a blade arranged in the cylinder chamber. The rotary fluid machine is used, e.g., as a compressor for compressing refrigerant circulating in a refrigerant circuit.
Japanese Patent Publication No. 2007-162555 discloses a rotary compressor as the rotary fluid machine of this type. In such a rotary compressor, an annular cylinder chamber is formed between outer and inner cylinders constituting a cylinder. The cylinder chamber is divided into outer and inner cylinder chambers by an annular piston, and each of the cylinder chambers is divided into high-pressure and low-pressure chambers by a blade. The annular piston is formed in a C-shape, i.e., a part of the annular ring splits, and swing bushes for connecting between the annular piston and the blade are provided at the split portion of the annular piston. The blade is formed separately from the cylinder in a rectangular flat shape. The blade is arranged so as to extend from the outer cylinder to the inner cylinder in a radial direction of the cylinder chamber at the split portion of the annular piston with the blade being detachably engaged in a blade groove formed in the cylinder. When eccentrically rotating the cylinder or the annular piston by a drive shaft, fluid is sucked into a low-pressure chamber side of each cylinder chamber, and then such fluid is compressed to be discharged from a high-pressure chamber side.